I've been researching this problem for a few days. I have a 555 timer for controlling a car heated windshield, and I'd like to have a single button controlling it, and use that same button to cancel mid-timer, if the user doesn't need the full duration.
I've so far come up with the following schematic, and have been testing on protoboard:
It has a 555 timer with around a 5 minute timer (doesn't need to be exact), and the output switches a mosfet configuration which turns on a relay. This relay then changes which line the switch pulls to GND from trigger to reset.
My problem is that when I have this circuit built, pushing the button causes the relay to energise, which pulls reset low before I can release the button, so the relay vibrates on and off rapidly, which gives an unpredictable output.
I think I might need to debounce the switch, but I am not sure what the best way to do this is (other than just putting a capacitor in parallel), and also I may need to delay the pull-down of the reset pin on the 555 so I don't end up with this vibrating effect, which I think is unrelated to the debouncing.
I've found this link which seems to do what I want, but I don't think the schematic they used is noticably different to the one I've designed.
Appreciate any help.